SCA-35 Selector Switch

OK Guys, please bare with me for a minute. I picked up a factory wired SCA-35. Upon inspection, I found one of the selector wafers is broken beyond repair, 3 parts, spent hours trying to fix it. Done with that.
Since this is a shorting type selector (for no cross talk between components) and made just for this amp, it is Irreplaceable so be careful with what you have. I started looking around and there is nothing that is compatable or, drop in ready. I contacted a couple companies that make selector switches, for them to R&D the switch is way to much $$$. Since the original is a double wafer switch, it is more akin to a 4 pole 5 throw switch. I purchased a couple of these Russian selectors seen below. I was thinking with a few modifications, It might work. Any thoughts would be greatly appreciated. Thanks, Tom

You might have more fun with an relay board, which may be bought cheap on ebay :
4 channels :
https://www.ebay.com/itm/Switch-Signal-Selector-Audio-Input-Signal-Amplifier-Board-Board-Relay-DIY/222466373655?hash=item33cc077817:g:Ao4AAOSw03lY554O

or 6 channels
https://www.ebay.com/itm/6-Channel-Unbalanced-Stereo-or-Balanced-Mono-Audio-Input-Selector-Relay-Module/201225517448?epid=1382862099&hash=item2ed9f9b988:g:bMMAAOSwBadTq6UA

Both may be rebuilt ( if not already ok) so the unused inputs are shorted to ground.
Board may be mounted at the back, switch mounts in it's usual place. 12V may be created by
doubling the filament.

Thanks peterh, I saw another post where you said this could work, I need to research the shorting or map it somehow. I understand the concept, implamenting it is the challenge.
Cool avatar by the way. Whats the story?

Tom_Johnson wrote:Thanks peterh, I saw another post where you said this could work, I need to research the shorting or map it somehow. I understand the concept, implamenting it is the challenge.
Cool avatar by the way. Whats the story?

The avatar is a graffiti made by an unknown artist in a railway tunnel. Long gone,
i think my fotos is the only memories. I found it appealing.

This is the side A Preamp

Finding a parts amp would be the easiest source. Finding a parts amp might be pretty difficult though. Long ago I had one but the parts are gone now.

I will check with a friend of mine who may have one.

Thanks WLT

https://www.alliedelec.com/electroswitch-inc-d2d-51/70152358/?mkwid=sjXpftxgT&pcrid=30980760979&pkw=&pmt=&gclid=CjwKCAiA9efgBRAYEiwAUT-jtCK3GM_b0n8UpwtjOMje5EIdpSW35vr97aaXnuGTF9715toTtpoaNRoCrqgQAvD_BwE

Long link - but you could actually create a replacement from OTC parts. A major PITA, but entirely possible.

I have gotten all sorts of stuff from this source - and adapted it with various combinations and permutations of surgery and jumpers:

https://www.surplussales.com/switches/SWRoMisc-2.html

Were I to find an SCA 35, I would be extremely hesitant to junk it, and far more likely to attempt to restore it.

Good luck with it!

Thanks Peter, I looked and if I could make a 10P5T, It could be done and have the tape head like the original. It is the grounding scheme that is so hard to replacate.

Rotary Switch
17P3T

Shorting functions built in, more than you need. And a 12-pole switch front-back.

You would use an X-Acto or similar to cut the traces as-needed to duplicate the pattern on the OEM.

Been-there-done-that. Fully agreed on the PITA part.

No spare part switch readily available. The parts amp should be at my friends place but buried and not easily found.

It was on a unit with no transformers, or covers. Not sure it even had circuit boards. But I remember it had some switches.

Sorry

Thanks WLT for looking around. I only need one waffer if anything turns up.

The other board will help me finish a conversion of a junk Pat 4 to some type of Pas preamp. I will know more when I get the boards. Looks like some trace cutting and Relay lifting may be involved. Better order a couple extra relays just in case.

that's the best and easiest solution, Dynaco always had to complicate things with their preamp switches,
I've always just tossed them in the trash and used a common 2P6T shorting rotary switch,
but you don't get the "special" connections that way, (does anyone use special connections anyway??)

Just ordered this for my SP14 build:

https://www.ebay.com/itm/Relay-4-way-audio-signal-switch-audio-input-selection-board-2-4-adjustable/132413895844?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2648

audiobill,
just a note for someone who might wonder why you do this . . .
so you are replacing a simple switch, for a simple switch connected to a bunch of relays.
Anyway, for the original thread, replacing a complex switch with a simple switch connected to a bunch of relays.

I guess I'd prefer that the actual audio connections take place inside a modern sealed relay switch than through a corroded, phenolic antique that was worn out decades ago....unless one believes that's the key to "vintage" sonics............the front panel switch is just a relay energizer, no audio involved.

tubes4hifi wrote:audiobill,
just a note for someone who might wonder why you do this . . .
so you are replacing a simple switch, for a simple switch connected to a bunch of relays.
Anyway, for the original thread, replacing a complex switch with a simple switch connected to a bunch of relays.
:D

Relays may be located right at the incoming connectors, no long wires hanging
across the amp. Short signal cables, That's a clear plus for me!

Relays are easily replaced if needed, and a future benefit is that they might be
remote controlled ( if needed=

The best relays i have found is mercury-wetted potted DIL relays. Unfortently mercury is banned
and those relays are unobtainable. The potted relay screen is easily interconnected by a grounding
strip, thus screening from outer hum sources or interferens.
The mere act of controlling them via 5V ( or 12V ) DC invites to easier control. One such example was
a before/after switch for not one but two tape recorders using only a on-off-on two pole switch.

peterh wrote:The best relays i have found is mercury-wetted potted DIL relays. Unfortently mercury is banned
and those relays are unobtainable. The potted relay screen is easily interconnected by a grounding
strip, thus screening from outer hum sources or interferens.
The mere act of controlling them via 5V ( or 12V ) DC invites to easier control. One such example was
a before/after switch for not one but two tape recorders using only a on-off-on two pole switch.

They are not banned in the US, and are readily available as current stock.

http://relays.struthers-dunn.com/viewitems/reed-relays/134-series-mercury-reed-relays

https://www.mouser.com/Search/Refine.aspx?Keyword=mercury+relay

And in Europe.

https://www.willow.co.uk/Mercury-Contactors/View-all-products.html

Not cheap.

Peter W. wrote:

peterh wrote:The best relays i have found is mercury-wetted potted DIL relays. Unfortently mercury is banned
and those relays are unobtainable. The potted relay screen is easily interconnected by a grounding
strip, thus screening from outer hum sources or interferens.
The mere act of controlling them via 5V ( or 12V ) DC invites to easier control. One such example was
a before/after switch for not one but two tape recorders using only a on-off-on two pole switch.

They are not banned in the US,  and are readily available as current stock.

http://relays.struthers-dunn.com/viewitems/reed-relays/134-series-mercury-reed-relays  

https://www.mouser.com/Search/Refine.aspx?Keyword=mercury+relay  

And in Europe.

https://www.willow.co.uk/Mercury-Contactors/View-all-products.html  

Not cheap.

That was good news ! Thanks !